N54 water pumps and N52 water pumps are identical. They're the same in the N55, 335iS and 1M as well. Only the M3 and 335d pumps are different in the 3 series.

How do you suggest calculating the number of hours run by each pump? As you said in a heat-sink situation mileage isn't the best data point but it is the only usable one really. From there you could split it into highway mileage or city mileage to account for the load times, but... too may people in here with cars they bought used and not knowing whether it was highway or city driven. Too many people who've had their cars since new and have driven a good mix of highway and city. Too many whose cars are FBO and are run harder, hotter, longer than a stock car. Too many people who let their cars idle for 30 minutes every morning under which circumstance lots of heat-sink and no mileage occurs.

Mileage is the only data point which is going to be standard across all of the pumps. Amount of heat sink is going to be different for every single car.

I think you made my point, then. There is no good way to determine a predictable failure rate, which means waiting for it to fail is the best solution. BMW should have built in a failure warning in the CBS to notify owners of pending water pump failure. But then that would be a percieved quality issue.

BTW the pumps for the N52 and N54 are different parts. The P/Ns are: 11517586925 (N52) and 11517563659 (N54). Just for the record.

basically what your graph is saying.. as your drive more (higher mileage) equal higher probability of Water pump failure.. but what about the people who flushed their coolant did that make any difference?

What can prevent the water pump failure? What about the replacement pumps are they any better?

Also what about the reliability of the t-stat (did people only saw WP failure only)? <= this is important because folks tend to change t-stat at the same time (to save future labor cost) but is it really required?

basically what your graph is saying.. as your drive more (higher mileage) equal higher probability of Water pump failure.. but what about the people who flushed their coolant did that make any difference?

The first plot shows that there is a peak in the chance of failure between 60-75k miles, and then drops off a bit. The drop could be due to driving style differences, or could indicate that some pumps are significantly more robust than others. Honestly, I have no idea of the reason.

The second plot give the probability of failing before a particular mileage is reached. There is still a lot of error, but obviously your chance of having a failure increases the more miles you drive.

Some people have had their pumps last well over 120k miles, but not many...

Quote:

Originally Posted by omerfar23

What can prevent the water pump failure? What about the replacement pumps are they any better?

I am not sure. flushing the coolant or cleaning the radiator can't hurt, but I don't think there is any real way to tell for sure. It may just be that the pumps fail regardless.

Once you pass 60,000 miles, it's probably best to make sure you have money stashed away in case you need to replace. (of course, always the case with any car)

Quote:

Originally Posted by omerfar23

Also what about the reliability of the t-stat (did people only saw WP failure only)? <= this is important because folks tend to change t-stat at the same time (to save future labor cost) but is it really required?

The vast majority of people have the WP fail before the t-stat, and as you said, replace the t-stat. They do occasionally fail, and do you really want to spend money and time tearing down again for what is a relatively cheap part relative to the labor required? I will personally replace it when the time comes.

basically what your graph is saying.. as your drive more (higher mileage) equal higher probability of Water pump failure.. but what about the people who flushed their coolant did that make any difference?

What can prevent the water pump failure? What about the replacement pumps are they any better?

Also what about the reliability of the t-stat (did people only saw WP failure only)? <= this is important because folks tend to change t-stat at the same time (to save future labor cost) but is it really required?

Coolant flushes will not affect the longevity of the pump. The pump control electonics fail due to heat loading.

I bought a 2006 330xi e90 USED at 107,000KM (60,000 miles). Can the dealer find out if my waterpump has been changed by the previous owner?

The dealer should be able to tell you all service that has been performed by BMW dealerships. Not for work done by the owner or independent shops, unless they put the service in the little maintenance book that comes with the car.

Quote:

Originally Posted by Efthreeoh

Coolant flushes will not affect the longevity of the pump. The pump control electonics fail due to heat loading.

Good to know. Will an inefficient cooling system or "old" coolant result in more heat load on the pump electronics? Or does the heat originate externally from the engine block/exhaust and not from the coolant fluid?

This gives the failure probability and the +/- 95% confidence intervals for that failure rate. Obviously, we need more data points to get more confidence, especially at higher mileages.

Keep voting!

Also, there will likely be a skew towards more failures given that many people with healthy water pumps may not check out the thread.

Plot of estimated failure rate during specific mileage intervals:

Plot of estimated failure rate before a specific mileage (perhaps more interesting to some of us):
(I didn't really propagate the uncertainty correctly, so the uncertainty is probably larger at higher mileages)

To be honest, even though I appreciate the effort here, I don't understand what the point is..

Second chart says that, as the part gets more use, the probability of it failing increases. Well we know that. Also, there is major 'undetermined' bias in the population of the data, where we don't know who we are not hearing from and who we really are hearing from (driver/maintenance etc habits, part specifics such as which cnc it was built in - long story there but I have seen failures of identical parts being produced in multiple cnc's and having different life due to placement of the cnc in the factory (i.e. exposed to afternoon sun or not).

So no offense or anything but unless the sample size is near 1% of N52s I would not draw any conclusions.

I think there is a simple conclusion and you do what you want with it;

There is a high level of probability to have a water pump failure after 70-100 k and the impact is very important. So, spending 350-400$ and a few hr to change the pump as prevention is not a bad idea.

To be honest, even though I appreciate the effort here, I don't understand what the point is..

Second chart says that, as the part gets more use, the probability of it failing increases. Well we know that. Also, there is major 'undetermined' bias in the population of the data, where we don't know who we are not hearing from and who we really are hearing from (driver/maintenance etc habits, part specifics such as which cnc it was built in - long story there but I have seen failures of identical parts being produced in multiple cnc's and having different life due to placement of the cnc in the factory (i.e. exposed to afternoon sun or not).

So no offense or anything but unless the sample size is near 1% of N52s I would not draw any conclusions.

I will be the first to agree with you that this is non-ideal. I am sure BMW know what the failure probabilities are, but it's not like they are talking.

It is unfortunate that there is some population bias, as in the people most likely to view the thread are ones searching for "water pump". There is also the so-called enthusiast bias, but whether that has a significant effect on pump life is questionable. But it is what it is, and it is about the best we can do in such a setting as this. I agree that we are likely getting over-estimates of the failure rate in the bins where we have a reasonable amount of data.

I view this more of an educational exercise and a curiosity for these very reasons. Regardless, it is interesting to know that I may only have a 30-40% chance of getting more than 100k miles on my water pump. Knowing this, I should reasonably expect a failure and should have educated myself on the warning signs/what to do (and educated my wife who often drives the car).

I would have liked to design the survey with many factors, but it is hard enough to get a reasonable number of response as is...

What can I say, I'm a data person, even if it is flawed. Althought flawed data in the wrong hands can be more dangerous than anecdotal evidence, I still prefer it.

Quote:

Originally Posted by woodpecka

I think there is a simple conclusion and you do what you want with it;

There is a high level of probability to have a water pump failure after 70-100 k and the impact is very important. So, spending 350-400$ and a few hr to change the pump as prevention is not a bad idea.

At the end, you decide if you want to take the risk..

I don't endorse preventative changing or not, as you said. I personally probably would not do it until close to 100k if at all, and that would be if I planned to keep the car for significantly longer. It depends on a lot, including warranty status, risk tolerance, and usage.

Ultimately, it sucks that there is a reasonably chance of getting stranded by a failure like this during the normal ownership period.

Agreed. Now what would be cool is if you were able to collect some data besides mileage and try and build a predictive model. I am a data person as well. I really would love to see predictive maintenance items as alerts in the vehicle. It would be a fair amount of software development but would be phenominal to have the car (who has all the data) to provide alerts/recommendations based on statistical data of its own.

Well in the case of the water pump, the ECU throws Shadow codes indicating the pump is starting to fail. These codes could be translated to a warning. What you suggest will never happen because it would make the car too easy to be repaired by a non BMW mechanic.